Spell check is on by default in Word, but you may need to turn it back on if you've disabled it

Microsoft Word checks your spelling as you type and marks mistakes with a red underline. This happens automatically in most cases — you do not have to do anything to start it. If you are not seeing red underlines under misspelled words, spell check is either turned off or set to ignore certain types of errors. The steps to turn it back on depend on whether you are using Word on Windows, Mac, or the web version.

Spell check works differently depending on which version of Word you have. The desktop versions (Word 2019, Word 2021, or Word as part of Microsoft 365) have more control options than the web version. If you share documents with others, turning spell check on or off affects only what you see on your screen — it does not change what other people see when they open the same file.

Key Takeaways

  • Spell check is turned on by default in Word, so if you do not see red underlines, it has been disabled in your settings.
  • On Windows, go to File > Options > Proofing and check the box next to "Check spelling as you type".
  • On Mac, go to Word > Preferences > Spelling and Grammar and select "Check spelling as you type".
  • In Word on the web, spell check cannot be turned off — errors always appear with red underlines, though you can ignore them individually.
  • Turning spell check on or off changes only what you see; other people viewing the document will see their own spell check settings.

How to turn on spell check in Word on Windows

Open Word and go to the File menu in the top left corner. Click on Options (near the bottom of the menu). In the Options window, click Proofing on the left side.

Look for the section labeled "Spelling" and find the checkbox next to "Check spelling as you type". If the box is empty, click it to turn spell check on. You will see a checkmark appear. Click OK at the bottom of the window to save your changes. Red underlines should now appear under misspelled words as you type.

If you want Word to ignore certain types of words — such as words in all capitals or words with numbers — you can check those boxes too. For example, checking "Ignore words in UPPERCASE" means Word will not flag acronyms like "NASA" or "COVID" as errors.

How to turn on spell check in Word on Mac

Open Word and click on Word in the menu bar at the very top of your screen. Select Preferences from the dropdown menu. In the Preferences window, click Spelling and Grammar.

Look for the checkbox next to "Check spelling as you type" and click it if it is empty. A checkmark will appear. Close the Preferences window by clicking the red circle in the top left corner. Spell check is now on, and you will see red underlines under misspelled words.

The Mac version also lets you choose whether to check grammar at the same time. If you want Word to flag grammar mistakes with a blue underline, check the box next to "Check grammar as you type" in the same window.

Spell check in Word on the web

Word on the web (also called Word Online) always has spell check turned on. You cannot turn it off through settings. Misspelled words appear with a red underline automatically as you type.

If you see a red underline and want to ignore it, right-click on the word and choose "Ignore All" to stop Word from flagging that word for the rest of the document. You can also click "Add to Dictionary" if the word is correct but Word does not recognize it — for example, a proper name or a technical term. Once you add a word to your dictionary, Word will recognize it in all future documents.

What to do if spell check is on but not working

If you have turned spell check on and still do not see red underlines, the document language setting may be wrong. Word checks spelling against the language you tell it the document is written in. If the language is set to something other than English, it will not catch English spelling mistakes.

To check the language, select all the text in your document (press Ctrl+A on Windows or Command+A on Mac). Go to Review in the menu bar, then click Language or Language Settings. Make sure the language is set to the version of English you use — usually "English (United States)" or "English (UK)". Click OK and spell check should now work.

Another reason spell check might not appear is if you have a very old version of Word or if your copy is not activated. If you are using Word 2010 or earlier, spell check works differently and may not be as visible. If your copy of Word shows "Not Licensed" or asks you to set up it, you may need to sign in with your Microsoft account or purchase a license.

How to turn off spell check if you want to

If red underlines are distracting and you want to turn spell check off, follow the same steps as turning it on — but uncheck the box instead of checking it. On Windows, go to File > Options > Proofing and uncheck "Check spelling as you type". On Mac, go to Word > Preferences > Spelling and Grammar and uncheck "Check spelling as you type".

You might want to turn spell check off if you are working with a document that contains many technical terms, code, or words in other languages that Word does not recognize. Even with spell check off, you can still right-click on any word and choose from spelling suggestions if you want to check a specific word.

Understanding red underlines versus other marks

A red underline means Word thinks the word is misspelled. A blue underline (if you have grammar check on) means Word thinks there is a grammar or style problem. A green underline is less common and usually means Word has detected a potential issue with clarity or tone.

Not every red underline means the word is actually wrong. Proper names, brand names, and technical terms often get flagged even though they are spelled correctly. You can right-click on the word and choose "Ignore All" to stop Word from flagging it, or "Add to Dictionary" to teach Word that this word is correct. Once you add a word to your dictionary, it will not be flagged in any of your documents going forward.

Frequently Asked Questions

Why does spell check not work on some words?

Word checks spelling against a built-in dictionary. If a word is not in that dictionary — such as a proper name, a brand name, or a technical term — Word will flag it even if it is spelled correctly. You can add these words to your personal dictionary so Word stops flagging them.

Does turning off spell check affect other people who open my document?

No. Spell check is a display setting that only affects what you see on your screen. When someone else opens your document, their own spell check settings will explore. If they have spell check on, they will see red underlines; if they have it off, they will not.

Can I turn spell check on for just one document?

No. The spell check setting applies to all documents you open in Word. If you turn it on, it stays on for every document until you turn it off again. However, you can ignore specific words in a single document by right-clicking and choosing "Ignore All".

What is the difference between spell check and grammar check?

Spell check looks for misspelled words (red underline). Grammar check looks for grammar and punctuation mistakes (blue underline). You can turn them on or off separately in the Proofing settings. Not all versions of Word have grammar check.

How do I add a word to my dictionary permanently?

Right-click on the word with the red underline and select "Add to Dictionary". That word will no longer be flagged in any document you open in Word. If you want to remove a word from your dictionary later, you will need to access your custom dictionary file, which is stored in your user folder — this is more technical and usually not necessary.